Gen2 - non-smooth running at constant throttle

[Minotaur]

Hi all. I am having a funny issue, and can't find anyone having it before.

At constant throttle and mostly on highway riding, it feels like the bike is about to stall. If you give it gas it accelerates (although not too smoothly). It does not die at low RPM, and idles fine.

I checked:
Coils - perfect
Spark plugs - good
Airbox/air filter - good.

Next up I plan to pull out the fuel pump and look for dirt in the tank and the teabag filter. Clean the injectors at the same time. One hint here is that the tank was painted after an accident, maybe crap stayed inside and contaminated the fuel system? Or that gas out of bottles in Mexico...

Anybody had this issue before or know a thread with information?

2014 model, 42000 miles.

Thanks,
Nick.

 

[Minotaur]

Btw, I also checked throttle body sync - also good

 

[WJBertrand]

When running a constant speed on level ground and smallish throttle openings, the engine will run on closed loop control which means the ECU is using the O2 sensor signal to adjust mixture. As soon as you open the throttle wide or engine RPMs rise above about 1/2 redline, the ECU will switch to open loop control and access the fixed fuel maps. Most engines also run open loop during warm up. The problem with closed loop running is that the ECU is trying to run the bike as lean as possible. This can cause lean surge which is what I think you're feeling. I remapping (reflash) of the ECU can fix this pretty cheaply. Anthony on this list and others offer this service for just a couple hundred bucks.

 

[Checkswrecks]

At the bottom of the throttle cables is the electronic throttle controller. You might clean/lube the cables and see if the controller is working right.

 

[Minotaur]

When running a constant speed on level ground and smallish throttle openings, the engine will run on closed loop control which means the ECU is using the O2 sensor signal to adjust mixture. As soon as you open the throttle wide or engine RPMs rise above about 1/2 redline, the ECU will switch to open loop control and access the fixed fuel maps. Most engines also run open loop during warm up. The problem with closed loop running is that the ECU is trying to run the bike as lean as possible. This can cause lean surge which is what I think you're feeling. I remapping (reflash) of the ECU can fix this pretty cheaply. Anthony on this list and others offer this service for just a couple hundred bucks.

Thanks Jeff. One thing I don't understand is, this issue only appeared recently and is slowly getting worse. From your description it sounds like a design issue that should have been noticeable all the time.

 

[Minotaur]

At the bottom of the throttle cables is the electronic throttle controller. You might clean/lube the cables and see if the controller is working right.

Thanks.I'll check this.

 

[WJBertrand]

Thanks Jeff. One thing I don't understand is, this issue only appeared recently and is slowly getting worse. From your description it sounds like a design issue that should have been noticeable all the time.

Dunno maybe lost a vacuum cap on one of the sync nipples??


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[richarddacat]

Sounds like you are on the right trail.